Effects of in-situ reactive phenolic resin on shape memory performance of polynorbornene

In this paper, resorcinol prepolymer (HT1005) in-situ reacted with hexamethoxymethyl melamine (HMMM, formaldehyde donor) to produce cured phenolic resin to modify polynorbornene (PNB) as a shape memory polymer (SMP). A moving die rheometer (MDR) was used to characterize the crosslinking degree of phenolic resin. Fourier transform infrared spectroscopy, differential scanning calorimeter, universal electronic tensile testing machine, dynamic mechanical analysis and X-ray diffraction was used to investigated the mechanical properties and shape memory performance of PNB composites. Infrared results showed that HT1005 reacted with HMMM forming a chemical cross-linking network in PNB. With the increase of HT1005 and HMMM, the phenolic resin network was gradually improved. When stress was applied to the composite, the phenolic resin rigid network first beared part of the external force, which improved the mechanical properties of the composite. When the content of HT1005 was too much, its dispersibility will become poor, and the rigid phenolic resin network will be too dense, which limited the recovery of PNB molecular chains. A small amount of HT1005 will be more uniformly dispersed in the PNB, the strength of the phenolic resin network was moderate, and the composite material had excellent shape memory and mechanical properties.

Automated summary

In this study, resorcinol prepolymer (HT1005) was used to modify polynorbornene (PNB) by reacting with hexamethoxymethyl melamine (HMMM) to produce cured phenolic resin. The mechanical properties and shape memory performance of PNB composites were investigated using various characterization techniques. The addition of HT1005 and HMMM improved the phenolic resin network in PNB, enhancing mechanical properties but excessive HT1005 hindered dispersibility and limited the recovery of PNB molecular chains, while optimum amount resulted in excellent shape memory and mechanical properties of the composite material.